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This report deals with the tests made on the hydroplaning phenomenon of car, truck and bus tires using the interior of a dynamic tire testing machine. For car tires, the relationship between braking force and slip ratio and between cornering force and slip angle as affected by hydroplaning were investigated. Studies were also made of the influence of the difference between radial-ply and cross-ply tires, inner pressure, load, thickness of the water film, etc.. Next, a study was conducted concerning the effect of hydroplaning on the cornering properties of truck and bus tires.

Dynamic properties of motorcycles are, to a great extent, governed by motorcycle tire properties. In this study, the influences of various factors such as, internal pressure, load, tire make, width, etc., on tire dynamic properties are clarified through the experiments carried out on laboratory testing machines. It was found that tire dynamic properties are significantly influenced by these factors, and the experiments yielded some beneficial data for the improvement of motorcycle dynamic properties as well as tire dynamic properties.

A tire vibration model which helps to clarify a vibration characteristics of radial tire in affecting vehicle ride quality and road noise is studied. The model is based on cylindrical beam on an elastic foundation, and cylindrical beam is characterized by bending stiffness, tension force and mass of tread band with breaker. Elastic foundation correspond to radial and tangential direction stiffness of side wall. The natural frequencies under inflation pressure are determined analytically by using of this model, further, measurement techniques of fundamental values in the model are examined and experimented. It is found that the analytical natural frequencies of radial tire agree well with the corresponding experimental results in a wide range of inflation pressure. Finally, an effect of foundamental values of tire on natural frequencies is discussed.

In order to obtain correction formulas applicable to aerodynamic force measurements in the JARI full-scale wind tunnel, correlation tests were carried in 1983 between the MIRA and JARI full-scale wind tunnel, with three different types of vehicle. The comparison of results, especially for zero-yaw-angle drag coefficient, shows that JARI measures, on the average, some 2.5 % above MIRA. The next year, in 1984, we investigated the causes of the difference in drag measurement between the two wind tunnels, and found that the most significant cause is a horizontal buoyancy due to static pressure gradient in the JARI test section which might be attributable to distortion in parts of the walls of the test section over many years.